Hey all! I am swapping a Ford 4.0 into a 1993 Miata and I am having some trouble with what I thought would be one of the simplest things, the fuel pump..

So the harness I have has the full fuel pump circuit system minus the inertia switch which I think got scrapped with the truck. but with a multi-meter I am getting the fuel pump power wire to show a priming signal.

I was under the impression from the wiring diagrams that the blue/red wire was the power wire that went from the Circuit Opening Relay (fuel pump relay in the miata) to the fuel pump harness but after trying it I've got no fuel pump still. Doing some more reading says the Miata fuel circuit sends a ground signal, not a power signal (I think).

So my questions:

1. Isn't there a test connector where I can jumper 2 pins together to run the fuel pump? (and if so where in the car would this connector be approximately in the car? Previous owner cut a lot of wiring so I don't have a lot of connectors in the engine bay..)

2.Can I tap into this circuit to simply power the fuel pump with my power lead coming from my Ford relay.

3. Did I do any damage to the fuel pump running 12 volts to the Blue/Red wire directly at the Circuit Opening Relay?

Thanks as always for any help or direction!
Alex

 

In the Monster Miata "kit" they have you install a jumper lead under the dash. Having seen several people have issues with that, I went another route. I would suggest that you wire the fuel pump circuit into the Ford ECU as shown in your Ford wiring book. I eliminated all of the Mazda wiring & fuel pump relay & replaced it with the much larger gauge wiring from the Ford along with the relay & inertia switch. If a problem ever arises it will be easier to diagnose because you can follow the Ford manual.

 

I am replacing the entire circuit with the Ford relay and I have the whole circuit working, my thought was to reuse the wiring that runs from the cabin back to the fuel pump since it was previously adequate and I am not doing any fuel system upgrades. However when I hooked up the Ford fuel pump relay to the Blue/Red wire from the ecu circuit opening relay I do not have a fuel pump priming..

I found out that I DO still have the diagnostic port so I will try and jumper that today and see if I have any pump problems.

 

That is what I did. Utilized the blue-red wire at that circuit opening relay to connect the Ford EEC fuel pump circuity to the fuel pump. Works fine.

I would try simply putting +12V on that lead to ensure it runs the pump. If it does, there is something in front of that I would guess that is not activating the fuel pump.